Electronic Circuit Diagram Schematic & PCB DesignThis is an active stereo tone control circuit using very well known op amp IC of TL072. The circuit include mic pre amp and mixer control. In this design, we have two inputs: one for line (stereo), one for microphone and has control of the three audio frequency (high treble, medium and low bass).Schematics | Free Online Schematic Drawing ToolSchematics is a free online schematic editor that allows you to create and share circuit diagrams.